Brushless motor system for power tools

ABSTRACT

A brushless DC (BLDC) motor is provided including a stator assembly and a rotor rotatably arranged inside the stator. The stator assembly includes a generally-cylindrical lamination stack including a stator ring and stator teeth extending radially inwardly from the stator ring towards a center bore, where the center bore is arranged to receive the rotor therein. The stator assembly further includes an end insulator disposed at an and of the lamination stack, where the end insulator includes a generally-cylindrical outer ring and teeth portions extending radially inwardly from the outer ring towards a center of the end insulator, and the outer ring and the teeth portion correspond to the stator ring and the stator teeth. Stator windings are wound around the stator teeth and the corresponding teeth portion of the end insulator. Each tooth portion includes an outer face having a sloped portion sloped at an angle in the direction of the outer ring of the end insulator to bias the stator windings towards the outer ring.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/241,385 filed Oct. 14, 2015, which is incorporated herein byreference in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates to cordless power tools. More particularly, thepresent invention relates to a high-power cordless power tool and abrushless motor for high-power cordless power tools.

BACKGROUND

Cordless power tools provide many advantages to traditional corded powertools. In particular, cordless tools provide unmatched convenience andportability. An operator can use a cordless power tool anywhere andanytime, regardless of the availability of a power supply. In addition,cordless power tools provide increased safety and reliability becausethere is no cumbersome cord to maneuver around while working on the job,and no risk of accidently cutting a cord in a hazardous work area.

However, conventional cordless power tools still have theirdisadvantages. Typically, cordless power tools provide far less power ascompared to their corded counterparts. Today, operators desire powertools that provide the same benefits of convenience and portability,while also providing similar performance as corded power tools.

Brushless DC (BLDC) motors have been used in recent years in variouscordless power tools. While BLDC motors provide many advantages overuniversal and permanent magnet DC motors, challenges exist inincorporating BLDC motors into many power tools depending on powerrequirements and specific applications of tool. The power componentsneeded for driving the BLDC motors in high power applications haveconventionally generated too much heat, making BLDC motors unfeasiblefor high-power power tools. This is particularly true for tools used inenvironments where dust and particulate from the workpiece is abundant,making it difficult to create a clean air flow within the tool to coolthe motor and associated components. These challenges need be addressed.

Furthermore, high power applications typically require larger motors. Aspower tools have become more ergonomically compact, it has become moredesireable to reduce the size of the motor while providing the requiredpower output.

SUMMARY

According to an embodiment of the invention, a brushless DC (BLDC) motoris provided including a stator assembly and a rotor rotatably arrangedinside the stator. In an embodiment, the stator assembly includes agenerally-cylindrical lamination stack including a stator ring andstator teeth extending radially inwardly from the stator ring towards acenter bore, where the center bore is arranged to receive the rotortherein. In an embodiment, the stator assembly further includes an endinsulator disposed at an and of the lamination stack, where the endinsulator includes a generally-cylindrical outer ring and teeth portionsextending radially inwardly from the outer ring towards a center of theend insulator, and the outer ring and the teeth portion correspond tothe stator ring and the stator teeth. In an embodiment, the statorassembly also includes stator windings wound around the stator teeth andthe corresponding teeth portion of the end insulator. In an embodiment,each tooth portion includes an outer face having a sloped portion slopedat an angle in the direction of the outer ring of the end insulator tobias the stator windings towards the outer ring.

In an embodiment, the sloped portion extends from approximately an innerend of the tooth portion towards the outer ring.

In an embodiment, the outer face of the tooth portion further includesflat portions along two longitudinal sides of the sloped portion. In afurther embodiment, the sloped portion occupies approximately a third ofa total width of the outer face of the tooth portion.

In an embodiment, the sloped portion includes an angle of 2 to 10degrees from the outer face of the tooth portion.

In an embodiment, the tooth portion occupies approximately an entirewidth of the outer face of the tooth portion.

In an embodiment, an end of the sloped portion near the outer ringincludes a recessed portion recessed from a plane of the outer face ofthe tooth portion.

In an embodiment, the outer face of the tooth portion further includes aflat portion located between an inner end of the tooth portion and thesloped portion. In a further embodiment, a radial length of the flatportion is 15% to 25% of the radial length of the sloped portion.

In an embodiment, the sloped portion includes a first sloped portionextending from approximately an inner end of the tooth portion at afirst angle with respect to the outer face of the tooth portion, and asecond sloped portion extending from the first sloped portion at asecond angle with respect to the outer face of the tooth portion that issmaller than the first angle.

In an embodiment, a power tool is provided including a housing and abrushless DC (BLDC) motor disposed within the housing, where the motorincluding a stator assembly and a rotor rotatably arranged inside thestator. In an embodiment, the stator assembly includes agenerally-cylindrical lamination stack including a stator ring andstator teeth extending radially inwardly from the stator ring towards acenter bore, where the center bore is arranged to receive the rotortherein. In an embodiment, the stator assembly further includes an endinsulator disposed at an and of the lamination stack, where the endinsulator includes a generally-cylindrical outer ring and teeth portionsextending radially inwardly from the outer ring towards a center of theend insulator, and the outer ring and the teeth portion correspond tothe stator ring and the stator teeth. In an embodiment, the statorassembly also includes stator windings wound around the stator teeth andthe corresponding teeth portion of the end insulator. In an embodiment,each tooth portion includes an outer face having a sloped portion slopedat an angle in the direction of the outer ring of the end insulator tobias the stator windings towards the outer ring.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings which form part of the specification:

FIG. 1 is a front perspective view of a power tool, in accordance withan embodiment;

FIG. 2 is a side view of the power tool partially showing internalcomponents of the power tool, in accordance with an embodiment;

FIGS. 3 and 4 depict front and rear perspective exploded view of thepower tool, in accordance with an embodiment;

FIG. 5 is another side view of the power tool, in accordance with anembodiment;

FIG. 6 is a rear perspective view of the power tool with filtersdetached, in accordance with an embodiment;

FIGS. 7A and 7B depict a cut-off perspective view of the tool 10 and anenlarged view of an intake conduit 52 of the air intake 36, with thefilter 38 in a detached position, respectively.

FIGS. 7C and 7D depict a cut-off perspective view of the tool 10 and anenlarged view of the intake conduit 52, with the filter 38 attached,respectively.

FIG. 8 is a perspective sectional view illustrating air flow through theair intakes, motor case and gear case assemblies, and exhaust vents, inaccordance with an embodiment;

FIG. 9 is a perspective view of the power tool additionally providedwith a flange holder, in accordance with an embodiment;

FIGS. 10A and 10B depict views of the flange holder, in accordance withan embodiment;

FIG. 11A is a rear perspective view of the motor assembly, in accordancewith an embodiment;

FIG. 11B is a front perspective view of the motor assembly, inaccordance with an embodiment;

FIG. 12 is a perspective exploded view of a motor assembly, inaccordance with an embodiment;

FIG. 13 is a perspective exploded view a stator assembly, in accordancewith an embodiment;

FIG. 14 is an enlarged sectional view of the stator assembly beingwound, in accordance with an embodiment;

FIG. 15A is a perspective view of an end insulator according to a firstembodiment;

FIG. 15B is a profile sectional view of a portion of the insulatoraccording to the first embodiment;

FIG. 16A is a perspective view of an end insulator according to a secondembodiment;

FIG. 16B is a profile sectional view of a portion of the insulatoraccording to the second embodiment;

FIG. 17A is a perspective view of an end insulator according to a thirdembodiment;

FIG. 17B is a profile sectional view of a portion of the insulatoraccording to the third embodiment;

FIG. 18A is a perspective view of an end insulator according to a fourthembodiment;

FIG. 18B is a profile sectional view of a portion of the insulatoraccording to the fourth embodiment;

FIG. 19A is a perspective view of an end insulator according to a fifthembodiment;

FIG. 19B is a profile sectional view of a portion of the insulatoraccording to the fifth embodiment;

FIG. 20A is a perspective view of an end insulator according to a sixthembodiment;

FIG. 20B is a profile sectional view of a portion of the insulatoraccording to the sixth embodiment;

FIG. 21A is a perspective view of an end insulator according to aseventh embodiment;

FIG. 21B is a profile sectional view of a portion of the insulatoraccording to the seventh embodiment;

FIG. 22A is a perspective view of an end insulator according to aneighth embodiment;

FIG. 22B is a profile sectional view of a portion of the insulatoraccording to the eighth embodiment;

FIGS. 23A-23D depict various perspective views of end insulatorsaccording to various additional or alternative embodiments;

FIG. 24 is an end view of the stator assembly including insulatinginserts, in accordance with an embodiment;

FIG. 25A is a perspective view of the stator assembly with insulatinginserts removed, in accordance with an embodiment;

FIG. 25B is a perspective view of the stator assembly with insulatinginserts installed, in accordance with an embodiment;

FIG. 26A depicts a partial cross-sectional view of the stator assemblywith an insulating insert, in accordance with an embodiment;

FIG. 26B depicts a partial perspective view of the stator assembly withinsulating inserts, in accordance with an embodiment;

FIG. 27 depicts a partial perspective view of the stator assembly withinsulating inserts in accordance with an alternative embodiment;

FIG. 28 depicts a partial perspective view of the stator assembly withinsulating inserts in accordance with yet another embodiment;

FIG. 29 depicts an axial view of the stator assembly with insulatinginserts in accordance with yet another alternative and/or additionalembodiment;

FIG. 30A depicts a partial cut-off perspective view of the motor housingincluding the seal member integrated therein, according to anembodiment;

FIG. 30B depicts a perspective view of the inside of the motor housingincluding the seal member integrated therein, according to anembodiment;

FIGS. 31A and 31B depict perspective views of the seal member alone,according to an embodiment;

FIG. 32 is a perspective view of the seal member mating with the statorassembly, in accordance with an embodiment;

FIGS. 33A and 33B depict perspective exploded views of a power moduleadjacent a motor housing, in accordance with an embodiment;

FIG. 34 depicts a perspective view of the assembled power moduleadjacent the motor housing, in accordance with an embodiment;

FIG. 35 depicts a perspective view of an alternative assembled powermodule adjacent an alternative motor housing, in accordance with anembodiment;

FIG. 36 is a partially-exploded perspective view of the motor housingand the power module, with insulator pads disposed therebetween, inaccordance with an embodiment;

FIG. 37A is an enlarged perspective view of the motor assembly showinginsulator pads disposed around input terminals, in accordance with anembodiment;

FIG. 37B is an enlarged perspective view of the motor assembly showinginsulator pads disposed between the motor housing and power module, inaccordance with an embodiment;

FIG. 38 is a perspective view of the motor assembly including inputterminals detached, in accordance with an embodiment; and

FIG. 39 is an enlarged perspective view of the motor assembly showinginput terminals attached to the power module, in accordance with anembodiment; and

FIG. 40 depicts a partially-exploded perspective view of the motorassembly showing the relative positions of the power module and therotor assembly, according to an embodiment;

FIG. 41 depicts a perspective view of the motor assembly showing therotor assembly outside the motor housing, according to an embodiment;and

FIG. 42 depicts a perspective view of the motor assembly showing therotor assembly fully assembled inside the motor housing, according to anembodiment.

Corresponding reference numerals indicate corresponding parts throughoutthe several figures of the drawings.

DETAILED DESCRIPTION

The following description illustrates the claimed invention by way ofexample and not by way of limitation. The description clearly enablesone skilled in the art to make and use the disclosure, describes severalembodiments, adaptations, variations, alternatives, and uses of thedisclosure, including what is presently believed to be the best mode ofcarrying out the claimed invention. Additionally, it is to be understoodthat the disclosure is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. The disclosure iscapable of other embodiments and of being practiced or being carried outin various ways. Also, it is to be understood that the phraseology andterminology used herein is for the purpose of description and should notbe regarded as limiting.

As shown in FIGS. 1-4, according to an embodiment of the invention, apower tool 10 is provided including a housing 12 having a gear case 14,a motor case 16, a handle portion 18, and a battery receiver 20. FIG. 1provides a perspective view of the tool 10. FIG. 2 provides a side viewof tool 10 including its internal components. FIGS. 3 and 4 depict twoexploded views of tool 10. Power tool 10 as shown herein is an anglegrinder with the gear case 14 housing a gearset (not shown) that drivesa spindle 24 arranged to be coupled to a grinding or cutting disc (notshown) via a flange (or threaded nut) 25 and guarded by a disc guard 26.It should be understood, however, that the teachings of this disclosuremay apply to any other power tool including, but not limited to, a saw,drill, sander, and the like.

In an embodiment, the motor case 16 attaches to a rear end of the gearcase 14 and houses a motor 28 operatively connected to the gear set 22.The handle portion 18 attaches to a rear end 30 of the motor case 16 andincludes a trigger assembly 32 operatively connected to a control module11 disposed within the handle portion 18 for controlling the operationof the motor 28. The battery receiver 20 extends from a rear end 31 ofthe handle portion 18 for detachable engagement with a battery pack (notshown) to provide power to the motor 28. The control module 11 iselectronically coupled to a power module 34 disposed substantiallyadjacent the motor 28. The control module 11 controls a switchingoperation of the power module 34 to regulate a supply of power from thebattery pack to the motor 28. The control module 11 uses the input fromthe trigger assembly 32 to control the switching operation of the powermodule 34. In an exemplary embodiment, the battery pack may be a 60 voltmax lithium-ion type battery pack, although battery packs with otherbattery chemistries, shapes, voltage levels, etc. may be used in otherembodiments.

In various embodiments, the battery receiver 20 and battery pack may bea sliding pack disclosed in U.S. Pat. No. 8,573,324, hereby incorporatedby reference. However, any suitable battery receiver and battery backconfiguration, such as a tower pack or a convertible 20V/60V batterypack as disclosed in U.S. patent application Ser. No. 14/715,258 filedMay 18, 2015, also incorporated by reference, can be used. The presentembodiment is disclosed as a cordless, battery-powered tool. However, inalternate embodiments power tool can be corded, AC-powered tools. Forinstance, in place of the battery receiver and battery pack, the powertool 10 include an AC power cord coupled to a transformer block tocondition and transform the AC power for use by the components of thepower tools. Power tool 10 may for example include a rectifier circuitadapted to generate a positive current waveform from the AC power line.An example of such a tool and circuit may be found in US PatentPublication No. 2015/0111480, filed Oct. 18, 2013, which is incorporatedherein by reference in its entirety.

Referring to FIG. 2, the trigger assembly 32 is a switch electricallyconnected to the control module 11 as discussed above. The triggerassembly 32 in this embodiment is an ON/OFF trigger switch pivotallyattached to the handle 18. The trigger 32 is biased away from the handle18 to an OFF position. The operator presses the trigger 32 towards thehandle to an ON position to initiate operation of the power tool 10. Invarious alternate embodiments, the trigger assembly 32 can be a variablespeed trigger switch allowing the operator to control the speed of themotor 28 at no-load, similar to variable-speed switch assembly disclosedin U.S. Pat. No. 8,573,324, hereby incorporated by reference. However,any suitable input means can be used including, but not limited to atouch sensor, a capacitive sensor, or a speed dial.

As shown in FIGS. 2-5, by housing the motor 28 and the power module 34substantially within the motor case 16 and beyond a gripping area of thehandle portion 18, the handle portion 18 can be ergonomically designedwithout regards to the physical constraints of the motor 28 and thepower module 34 to provide the operator with a more comfortable andeffective operation and balance of the power tool during operation. Forinstance, the handle portion 18 can be provided with reduced girth andcontoured for easier and more comfortable gripping by the operator toreduce the user's hand fatigue.

As shown in FIG. 5, in various embodiments, the handle portion 18 canhave a circumference of approximately 110 to 140 mm (more preferably 120to 130 mm, e.g. approximately 125 mm) measured at line A proximate therear end 31 of the handle portion 18, a circumference of approximately120 to 150 mm (more preferably 130 to 140 mm, e.g. approximately 135 mm)measured at line B at about a mid-point 33 between the end 31 of thehandle portion 18 and the trigger assembly 32, and a circumference ofapproximately 140 to 190 mm (more preferably 150 to 180 mm, e.g.,approximately 165 mm) measured at line C at the position of the triggerassembly 32. By contrast, the circumference of the motor case 16 thathouses the motor 28 may be over approximately 200 mm, e.g., 245 mm, asmeasured at line D. This arrangement represents a motor case 16 tohandle portion 18 girth ratio of approximately 1.5× to 2×, according toan embodiment.

As mentioned above and discussed later in detail, according to anembodiment, power tool 10 described herein is high-power power toolconfigured to receive a 60V max battery pack or a 60V/20V convertiblebattery pack configured in its 60V high-voltage-rated state. The motor28 is accordingly configured for a high-power application with a statorstack length of approximately 30 mm. Additionally, as later described indetail, the power module 34, including its associated heat sink, islocated within the motor case 16 in the vicinity of the motor 28. Asshown in FIG. 5, the relative positions and weight of the gear case 14and the motor case 16 including the motor 28 and power module 34 allowsthe center of gravity of the tool 10 with the battery pack attached tothe battery receiver 20 to be within the tool handle 18 substantiallyclose to the trigger 32, despite the heavy weight of the 60V batterypack. Specifically, while using a 60V pack with conventional grinderswould place the center of gravity of the tool at the foot of the handleportion 18 near the battery receiver 20 due to the heavy weight of thebattery pack, according to an embodiment the center of gravity is aroundin close proximity to the trigger 32, i.e., at point E substantially inline with the operator's wrist as the operator grabs the handle portion32, which reduces hand fatigue and balances the tool 10 within theoperator's hand. In an exemplary embodiment, handle portion 18 has alength of about 130-170 mm (e.g., 150 mm), and the motor case 16 withmotor 28 has a length of about 70-100 (e.g., 84 mm), which represents ahandle portion 18 to motor case 16 length ratio of approximately 1.3× to2.5×, preferably 1.6× to 2×, more preferably 1.7× to 1.8×, according toan embodiment.

The embodiments described herein provide a high-power portable cordlesspower tool 10, such as a grinder, that operates with a high voltagebattery pack, for example, a battery pack having a maximum voltage ofapproximately 60V or nominal voltage of approximately 54V, and producesmaximum power output of over 1600 Watts, a maximum torque of over 30inch-pounds (ln*Lbs) and maximum speed of over 8000 rotations-per-minute(RPM). No cordless grinder currently in the marketplace provides suchperformance parameters, particularly from a small grinder havinggeometric ergonomics described above.

Another aspect of the invention is discussed herein with reference toFIGS. 6-8 and continued reference to FIGS. 1-5. As discussed brieflyabove and later in detail, power module 34 is provided within the motorcase 16 near the motor 28, or at the end of the handle portion 18 nearthe motor case 16. As it is well known in the art, power module 34switching arrangement generates a considerable amount of heat thatshould be carried away from the motor case in an effective manner.

According to an embodiment, referring to FIGS. 2 and 6-8, the motor case16 defines a pair of generally oblong air intakes 36 around a peripheryof the power module 34. The air intakes 36 are arranged to direct airflow into the motor case 16 in a manner that air is circulated aroundthe power module 34 as well as the motor 28. In an embodiment, airintakes 36 are sized and shaped to receive a corresponding pair of airfilters 38 and extend the majority of the circumference of the motorcase 16. The intakes 36 are positioned radially about the rear end 30 ofthe motor case 16 adjacent to the handle 18, and generally correspondingwith the position of the power module 34. Positioning the intakes 36forward of the handle portion 18 locates them generally away from thenormal trajectory of the grinding particulate caused by grindingoperation on a work piece, thus lessening the ingestion of grindingparticulate and increasing service and reliability of the tool.

In addition, in an embodiment, each air intake 36 includes a pluralityof intake conduits 52 arranged to receive and direct air from outsidethe tool 10 into the motor case 16. Intake conduit 52 are defined by(and separated via) axial walls 53 provided axially within the airintake 36, and an acruate baffle 54 described below. The angularorientation of the baffles 54 within the intake conduits 52 results in apath of air flow outside the air intakes 36 that is considerablydifferent from the path of the particulate stream caused by the grindingoperation on the work piece, and thus prevents a direct path by for theparticulate stream to enter into the intakes 36.

Referring to FIG. 6, each filter 38 can include two generally oblongbands 42 with a plurality of ribs 44 extending therebetween. Theplurality of ribs 44 generally correspond to the axial walls 53 of theair intakes 36. Each filter 38 further includes filter material 46extending between the bands 42. The filter 38 is arcuate along itslength to correspond with intakes 36. In an embodiment, each filter 38includes a pair of retaining tabs 48 extend inwardly from each end ofthe filter 38 that securely mate with (e.g., snap-fit into) the edges ofintakes 36. Each filter 38 may further include a pin 50 extendinginwardly from a midpoint of the filter 38 that fits into a correspondinghole 51 provided within the intakes 36. The filters 38 provide furtherlimit entry of contamination, debris, and grinding particulate fromentering through the intakes 36.

FIGS. 7A and 7B depict a cut-off perspective view of the tool 10 and anenlarged view of the intake conduit 52 of the air intake 36, with thefilter 38 in a detached position, respectively. FIGS. 7C and 7D depict acut-off perspective view of the tool 10 and an enlarged view of theintake conduit 52, with the filter 38 attached, respectively.

As shown in these figures, acruate baffle 54 of the air intake 36extends from a rear edge 59 of the air intake 36 at an angle withrespect to an axis of the tool 10, inwardly towards the motor 28. Formedbetween a distal end 57 of the acruate baffle 54 and a front edge 56 ofthe air intake 36 are inlets 55 radially arranged and separated viaaxial walls 53. During operation, the arcuate shape and the angularorientation of the baffle 54 effectively directs incoming air in thedirection of the motor 28, thus created an air flow path outside thetool 10 that is considerably different from the path of the particulatestream caused by the grinding operation.

In an embodiment, airflow through the air intake 36 is generated viamotor fan 37, which is rotatably attached to the motor 28. Inconventional designs, where power components are disposed within thehandle portion 18, it is important for the air flow generated by themotor fan to circulate through the handle portion 18 as well as themotor case 16 in order to cool the power components and the motor. Inthe above-described embodiment, by contrast air intakes 36 arepositioned near a rear end 30 of the motor case 16 and in much closerproximity to the fan 37 and exhaust vents 58. The reduced distancebetween the intakes 36, fan 37, and exhaust vents 58 provide better airflow efficiency around the power module 34 and the motor 28, whichgenerate the most heat, bypassing the control unit 11 and othercomponents within the handle portion 18 that do not generate aconsiderable amount of heat. In the present exemplary embodiment, whilethere is still some air leakage through the battery receiver 20 and thehandle portion 18, the airflow through the handle portion 18 is reducedto about 0-2 Cubic Feet per Minute (CFM), which is less than 10% of thetotal air flow that enters the motor case 16, while over 90% of thetotal airflow (e.g., 15-17 CFM) is entered through the air intakes 36.

FIG. 8 depicts a partial perspective view of tool 10, including acut-off view of the motor 28, and air flow paths entering the motor case16 through the air vents 36. As shown in this figure, the incoming airentering through the air intakes 36 circulates the power module 34,particularly around the heat sink, before entering the motor 28. The airthen circulates around the motor shaft, the rotor and the stator (aswill be described later in detail) before exiting through the exhaustvents 58. Some of the outgoing air also exits through the gear case andaround the spindle (not shown).

Another aspect of the disclosure is described herein with reference toFIGS. 9, 10A and 10B.

In conventional power tools, such as grinders, that use rotaryaccessories, it is common practice to fixedly attach the accessory tothe spindle via a backing plate and a threaded nut (referred to as aflange set) provided with the power tool. Alternatively the accessoryitself integrally includes a threaded insert that eliminates the needfor a flange set. In use, tool operators may variously switch betweendifferent grinding and cutting accessories, some of which may require aflange set and some may include integral threads. In practice, theseparation of the tool from the flange set may lead to the flange setbeing lost or misplaced.

According to an embodiment, to overcome this problem, a flangeattachment mechanism is provided on power tool 10 to provide theoperator the ability to attach the flange set 25 to the tool 10 at anauxiliary location when the flange set 25 is not needed, i.e., when anaccessory with integral threaded insert is being used on the tool 10,without inhibiting the operator's ability to use the power tool 10. Asshown in FIG. 9, in an embodiment, a flange holder 400 is provided atthe foot of the power tool 10, e.g., on a side of the battery receiver20. The flange holder 400 may alternatively be provided at the end ofthe handle portion 18, under the motor case 16, or any other suitablelocation where it does not interfere with the operator's handling of thetool 10. Alternatively, if tool 10 is a corded tool, the flange holder400 may be provided on the cord.

FIGS. 10A and 10B depict front and back perspective views of the flangeholder 400. As shown herein, flange holder 400 includes a threadedportion 402 extending from a base portion 404. A back side of the baseportion 404 includes pin-shape inserts 406 and a flexible projection 408arranged to be received or snapped into corresponding openings orretaining features on the tool 10 battery receiver 20. When tooloperator is not using the flange set 25, he or she may tighten theflange set 25 onto the flange holder 400.

Various aspects of the disclosure relating to the motor 28 are discussedherein.

FIGS. 11A and 11B depict two perspective views of motor 28, according toan embodiment. FIG. 12 depicts an exploded view of the motor 28,according to an embodiment. As shown in these figures, the motor 28 is athree-phase brushless DC (BLDC) motor having a can or motor housing 29sized to receive a stator assembly 70 and a rotor assembly 72. Variousaspects and features of the motor 28 are described herein in detail. Itis noted that while motor 28 is illustratively shown in FIGS. 1-9 as apart of an angle grinder, motor 28 may be alternatively used in anypower tool or any other device or apparatus.

In an embodiment, rotor assembly 72 includes a rotor shaft 74, a rotorlamination stack 76 mounted on and rotatably attached to the rotor shaft74, a rear bearing 78 arranged to axially secure the rotor shaft 74 tothe motor housing 29, a sense magnet ring 324 attached to a distal endof the rotor shaft 74, and fan 37 also mounted on and rotatably attachedto the rotor shaft 74. In various implementations, the rotor laminationstack 76 can include a series of flat laminations attached together via,for example, an interlock mechanical, an adhesive, an overmold, etc.,that house or hold two or more permanent magnets (PMs) therein. Thepermanent magnets may be surface mounted on the outer surface of thelamination stack 76 or housed therein. The permanent magnets may be, forexample, a set of four PMs that magnetically engage with the statorassembly 70 during operation. Adjacent PMs have opposite polarities suchthat the four PMs have, for example, an N-S-N-S polar arrangement. Therotor shaft 74 is securely fixed inside the rotor lamination stack 76.Rear bearing 78 provide longitudinal support for the rotor 74 in abearing pocket (described later) of the motor housing 29.

In an embodiment, fan 37 of the rotor assembly 72 includes a back plate60 having a first side 62 facing the motor case 16 and a second side 64facing the gear case 14. A plurality of blades 66 extend axiallyoutwardly from first side 62 of the back plate 60. Blades 64 rotate withthe rotor shaft 44 to generate an air flow as previously discussed. Whenmotor 28 is fully assembled, fan 37 is located at or outside an open endof the motor housing 28 with a baffle 330 arranged between the statorassembly 70 and the fan 37. The baffle 330 guides the flow of air fromthe blades 64 towards the exhaust vents 58.

In an embodiment, power module 34 is secured to another end of the motorhousing 29, as will be described later in detail.

Referring now to the exploded view of FIG. 13 and with continuedreference to FIG. 12, in an embodiment, stator assembly 70 includes agenerally cylindrical lamination stack 80 having center bore 88configured to receive the rotor assembly 72. Lamination stack 80 furtherincludes a plurality of stator teeth 82 extending inwardly from a statorring 83 towards the center bore 88. The stator teeth 82 define aplurality of slots 84 therebetween configured. A plurality of coilwindings 86 are wound around the stator teeth 82 into the slots 84. Thestator teeth 82 are generally rectangular-shaped with two tips 85extending from an end portion 87 thereof. Each slot 84 is generallytrapezoidal shaped with a gap 91 extending between opposing tips 85 ofend portions 87 of each pair of teeth 82. An insulating shield 90 isreceived within each stator slot 84 and generally surrounds each winding86 to electrically insulate the winding 86 from the lamination stack 80.In various instances, the insulating shield 90 can be made from flexibleinsulating material such as paper material.

In various embodiments, stator assembly 70 further includes a first endinsulator 92 and second end insulator 94 attached to respective ends ofthe lamination stack 80 using any suitable method, such as, snap fit,friction fit, adhesive, or welding to provide electrical insulationbetween the windings 86 and the lamination stack 80. Each end insulator92 and 94 generally corresponds to the shape of end laminations on thelamination stack 80 so that it generally covers the end of thelamination stack 80. In an embodiment, each insulator includes agenerally cylindrical outer ring 96 corresponding to the stator ring 83,with a plurality of tooth portions 98 extending inwardly from the outerring 96 towards the center of the end insulator 92 and 94. Each toothportion 98 is generally shaped to cover a corresponding tooth 82 of thestator 70 with side walls 100 extending axially inwardly into statorlamination slots 84 for proper alignment and retention of the endinsulators 92 and 94 at the ends of the lamination stack 80, as well asproviding further electrical insulation within the slots 84. A tab 102extends outwardly away from the lamination stack 80 from an end 101 ofeach tooth portion 98 corresponding to end portion 87 of respectivestator teeth 82. The first end insulator 92 includes a plurality ofretention members 108 that defines receiving slots 106 for receiving theinput terminals 104, as described later in detail.

Referring now to FIG. 14, a partial radial view of the stator laminationstack 80 during a winding of stator windings 86 is depicted, accordingto an embodiment. Generally, during the winding process of the statorwindings 86, two routers T of a winding machine (not shown) movedlongitudinally back and forth within the slots 84 to wind the statorwindings 86 around stator teeth 82. Generally, as the windings 86 arewound, they stack on top of each other around a center portion of thecorresponding tooth 82 within the slots 84, leaving gaps between thewindings 86 and the stator ring 83. This limits the amount of coil thatcan be wound within each slot 84, which adversely impacts motor poweroutput.

Referring now to FIGS. 15A to 23D, with continued reference to FIG. 13,in order to maximize the amount of coil wound in stator slots 84,according to an embodiment of the invention, the tooth portions 98 ofthe end insulators 92, 94 are contoured to include a sloped profileconfigured to bias the windings 86 away from a center bore 88 of thestator lamination stack 80 and towards the outer circumference of thestator lamination stack 80 (i.e., stator ring 83) while the windings 86are being wound around the stator teeth 82. Specifically, as the windingwire is wound around the teeth portions 98 of the end insulators 92, 92at longitudinal ends of the stator teeth 82, the sloped profile of theteeth portions 98 slidingly bias the winding wire in the direction ofthe slope and towards the outer ring 96. Various profiles of the teethportions 98 are discussed herein, according to various embodiments.

In a first embodiment shown in FIG. 15A and the partial side view ofFIG. 15B, each tooth portion 98 includes a sloped portion 112 extendingat an angle from the tab 102 downwardly towards the outer ring 96, andgenerally flat portion 110 extending around the sloped portion 98 fromthe tab 102 to the outer ring 96. In an embodiment, the sloped portion112 may occupy approximately a third of the total width of the toothportion 98. In an embodiment, the sloped portion 112 may extend at anangle of, e.g., 2 to 10 degrees.

In the second embodiment shown in FIG. 16A and the partial side view ofFIG. 16B, each tooth portion 98 includes a sloped portion 122 extendingat an angle from the tab 102 downwardly towards the outer ring 96. Thesloped portion 122 may occupy approximately the entire total width ofthe tooth portion 98. An end portion 124 of the sloped portion 112 nearthe outer ring 96 may slightly recessed by, e.g., 0.2 to 2 mm, from aplane of the outer ring 96. Furthermore, in an embodiment, a flatportion 126 may additionally be arranged between the tab 102 and thesloped portion 122. A radial length of the flat portion 126 may be lessthan the radial length of the sloped portion 122, for example, 10% to40%, preferably 15% to 25%, of the radial length of the sloped portion122. The sloped portion 112 may extend from the flat portion 126 at anangle of, e.g., 5 to 15 degrees. In an embodiment, sloped portion 112may be laterally flat or may include a laterally arcuate surface.

In the third embodiment shown in FIG. 17A and the partial side view ofFIG. 17B, each tooth portion 98 includes a sloped portion 132, arecessed end portion 134, and a flat portion 136, similarly to thesecond embodiment described above, but a radial length of the flatportion 136 is approximately close to or greater than the radial lengthof the sloped portion 132. For example, the radial length of the flatportion 136 may be over 40%, preferably 50% to 60%, the radial length ofthe sloped portion 132. The sloped portion 112 may extend at an angleof, e.g., 5 to 20 degrees.

The fourth embodiment shown in FIG. 18A and the partial side view ofFIG. 18B is a combination of the first and the second embodiments.Specifically, in this embodiment, each tooth portion 98 includes a firstsloped portion 142, a recessed end portion 144, and a flat portion 146,similarly to the second embodiment described above. In addition, eachtooth portion 98 includes a second sloped portion 148 similar to slopedportion 112 of the first embodiment. The second sloped portion 148extends from the tab 102 over a middle portion of the flat portion 146and the first sloped portion 142, at an angle that is greater than theangle of extension of the first sloped portion 142. In an embodiment,the second sloped surface 148 may have an angle of 1 to 10 degrees withrespect to the first sloped surface 142.

The fifth embodiment shown in FIG. 19A and the partial side view of FIG.19B is similar to the fourth embodiment above, but the second slopedsurface 158 has a greater extension angle. In an embodiment, the secondsloped surface 158 may have an angle of 10 to 20 degrees with respect tothe first sloped surface 152.

The sixth embodiment shown in FIG. 20A and the partial side view of FIG.20B is a combination of the first and the third embodiments.Specifically, in this embodiment, each tooth portion 98 includes asloped portion 162, a recessed end portion 164, and an extended flatportion 166, similarly to the third embodiment described above. Inaddition, each tooth portion 98 includes a second sloped portion 168similar to sloped portion 112 of the first embodiment. The second slopedportion 168 extends from the tab 102 over a middle portion of the flatportion 166 and the first sloped portion 162, at an angle that isgreater than the angle of extension of the first sloped portion 142. Inan embodiment, the second sloped surface 148 may have an angle of 10 to20 degrees with respect to the first sloped surface 142.

The seventh embodiment shown in FIG. 21A and the partial side view ofFIG. 21B is similar to the sixth embodiment above, but the second slopedsurface 178 has a smaller extension angle. In an embodiment, the secondsloped surface 178 may have an angle of 0 to 10 degrees with respect tothe first sloped surface 152. The eighth embodiment of shown in FIG. 22Aand the partial side view of FIG. 22B, is similar to the firstembodiment described above, except that sloped portion 182 extendsangularly from the outer ring 96 to a flat portion 184 disposed betweenthe sloped portion 182 and the tab 102. In an embodiment, the slopedportion 182 may have an angle of 20 to 30 degrees with respect to aplane of the outer ring 96.

FIGS. 23A-23D depict several other alternative embodiments of the endinsulator 92 having various combinations of sloped surfaces discussedabove.

Another aspect of the invention is described herein with reference toFIGS. 24 to 29.

Referring to FIG. 24, in the present embodiment, an axial view of thestator assembly 70 including lamination stack 80, radial ends 101 ofstator teeth 82, and stator windings 86 wound around stator teeth 82,according to an embodiment.

Each winding 86 is distributed around the lamination stack 80 to form aneven number of poles. For instance, in a three-phase stator, eachwinding 86 includes a pair of windings arranged at opposite ends of thelamination stack 80 to face each other. The windings 86 may be connectedin a variety of configurations, such as, a series delta configuration, aparallel delta configuration, a series wye configuration, or a parallelwye configuration. Although the present embodiment depicts a respectiveset of three windings, three retention members, and three inputterminals, any suitable number can be used.

In high power applications, e.g., power tools powered by 120V batterypacks or 120V AC power, there are regulatory requirements imposed bysafety organizations, i.e., Underwriters Laboratories (“UL”), oninsulating distance required between one conductive surface to another.In the stator assembly 70, the stator windings 86 are insulated from thestator lamination stack 80 via insulating shield 90 previouslydiscussed, but UL standards require 2 mm of insulation clearance betweenthe windings 86 and the exposed area of the stator lamination stack 80,i.e., at the tips 85 of stator teeth 82.

In order to provide sufficient insulation between the tips 85 of statorteeth 82 and the stator windings 86, according to an embodiment of theinvention as shown in perspective views of FIGS. 25A and 25B, andzoomed-in views of FIGS. 26A and 26B, a plurality of generallyrectangular insulating inserts 260 (also referred to as slot wedges) areinserted at respective gaps 91 between the teeth 82. FIG. 26A depicts across-sectional view of the stator assembly 70 without the endinsulators 92, 94, whereas FIG. 26B depicts a perspective view of thestator assembly 70 including the end insulator 92. The insulatinginserts 260 laterally push and bias the windings 86 generally outwardlyaway from the tips 85 of the stator teeth 82.

While slot wedges are conventionally used in universal motor armatures,insulating inserts 260 are inserted directly above the gaps 91 withineach slot 84 of the stator 70 such that each end of the insulatinginsert 260 is fitted between a tip 85 of the stator tooth 82 and thestator windings 86. The insulating inserts 260 bias and displace thewindings both radially and circumferentially such that, when inserted,the insulating inserts 260 provide a predetermined clearance between thewindings 86 and the tips 85 of the teeth 82, as required for compliancewith UL standards.

In addition, in an embodiment, the insulating inserts 260 may beinserted under the insulating shield 90, i.e., between the ends of theshield 90 and the teeth tips 85, to displace the insulating shield 90laterally as well. In various embodiments, the predetermined clearanceis at least equal to the minimum clearance specified under UL standardsfor high voltage tools (e.g., 2 mm). As arrow 261 of FIG. 26A, thisclearance is measured from the tip 85 of the tooth 82, around theinsulating insert 260 and the tip of the insulating shield 90, to thewindings 86. It is noted that the distance is not measured as a straightline between the tooth 82 and the windings 86.

In an embodiment, in addition to providing electrical insulation betweenthe stator lamination stack 80 and the stator windings 86, theinsulating inserts 260 effectively form a mechanical seal between thestator assembly 70 and the rotor assembly 72 to prevent airflowtherebetween. During operation, the insulating inserts 260 substantiallyprevent air, including particles and contamination, from flowing throughthe gaps 91 between the end portions 87 of stator teeth 82 (see FIG.13), effectively isolating the paths of air flow through the rotorassembly 72 and the stator assembly 70. This arrangement reduces thechances of air particulate and contamination from bouncing off the rotorassembly 72 at high speed and hitting the stator windings 86, whichwould cause substantial damage to the stator windings 86. In anembodiment, insulating inserts 260 may be made of paper or plasticmaterial.

In an embodiment, as shown in FIGS. 26B and 26C, for end insulator 92,94 (only end insulator 92 shown herein), tips 103 of end portions 101 ofthe end insulator tooth 98 include guides 105 that engage the sides ofthe insulating inserts 260 and facilitate the insertion of theinsulation inserts 260 between the tips 85 of the stator teeth 82 andthe insulating shield 90. The guides 105 make it easier for theinsulating inserts 260 to be inserted during the assembly process.

FIG. 27 shows an alternative embodiment of the invention, whereinsulating inserts 264 are provided as beaker shaped wedges that can beinserted, such as with a form-fit and/or friction-fit, into respectivestator slots 84. The inserts 264, includes a wedge portion 263 that,similarly to the above-described embodiment, bias the windings 86laterally and outwardly to provide a predetermined clearance between thewindings 86 and the stator teeth 82. The inserts 264 in this embodimentadditionally include a radially extending portion 265 that extend fromthe wedge portion 263 toward the stator ring 83 of the stator laminationstack 80 and engage an inner surface of the stator ring 83 within theslot 84. In this manner, the radially extending portion 265 securelyholds the wedge portion 263 in place.

FIG. 28 depicts yet another embodiment, where insulating inserts 364 areprovided with a substantially U-shaped or rectangular-shaped middleportion 366 arranged to be received between respective tips 85 ofadjacent stator teeth 82. The middle portion 366 may be insertedform-fittingly and/or friction-fittingly inside the gap 91 extendingbetween opposing tips 85 of end portions 87 of each pair of teeth 82 ina way to securely retain the wedge portions 368 in place between thestator windings 86 and the tips 85 of stator teeth 82, as describedabove.

FIG. 29 depicts yet another embodiment, where insulating inserts 374have a rectangular-shaped or U-shaped middle portion 376 and wedgeportions 378, as described above, but additionally includes a projection379 opposite the middle portion 376 to further straighten insulationinserts 374.

Another aspect of the invention is described herein with reference toFIGS. 30A to 32.

As described to above, insulating inserts 260, 263, 364, 374mechanically seal the gaps 91 between the stator teeth 82, thussubstantially preventing flow of air between the stator windings 86 andthe rotor assembly 72 over the length of the stator lamination stack 80.However, at ends of the stator assembly 70, particularly at the one ofend of the stator housing 70 close to the air intakes 36 where the airfirst enters the motor 28, due to the arcuate shape of the ends of thestator windings 86 and the tabs 102 of the end insulator 92, air canstill leak from the stator assembly 70 to the rotor assembly 72 and viceversa. In order to overcome this deficiency, according to an embodimentof the invention, a cylindrical seal member 268 is provided at the endof the stator assembly 70, described herein.

FIG. 30A depicts a partial cut-off perspective view of the motor housing29 including the seal member 268 integrated therein, according to anembodiment. FIG. 30B depicts a perspective view of the inside of themotor housing 29 including the seal member 268 integrated therein,according to an embodiment. FIGS. 31A and 31B depict perspective viewsof the seal member 268 alone, according to an embodiment. In thesefigures, the rear end 267 of the motor housing 29 defines a generallycylindrical rear bearing pocket 266 disposed to receive rear bearing 78of the rotor assembly 72, previously described. The motor housing 29further includes, round a periphery of the bearing pocket 266 and in anaxial direction of the motor housing 29 towards the motor 28, acylindrical sealing member 268. In an embodiment, the sealing member 268includes a crown-shaped cylindrical portion 270 terminating with anannular mating surface 272 defining generally arcuate or semi-circularindents 274 that correspond to the shape of windings 86 and separated bycrown teeth 276. In an embodiment, the inner surface 278 of crown teeth276 tapers outwardly, thereby reducing the thickness of crown teeth 276as they approach the end mating surface 272, effectively forming a wedgeor chamfer that enhance the mechanical seal between the windings 86.Those skilled in the art will recognize that other configurations of thecrown teeth 276 can be used, including, but not limited to, rectangular,curved, triangular, and the like. Also, other configurations of theindents 274 can also be used, including to, but not limited to, square,rectangular, curvilinear, and the like. Furthermore, those skilled inthe art will recognize that while sealing member 268 is shown as anintegral part of the motor housing 29, sealing member 268 may beprovided, integrally or as a separate piece, within any part of thetool, e.g., the tool housing.

As shown in FIG. 32, when the motor 28 is assembled into the motorhousing 29, the arcuate or generally semi-circular indents 274 mate withthe ends of the stator windings 86, tabs 102 of the end insulator 92, orthe area in between the stator windings 86 and the tabs 102. Meanwhilethe crown teeth 276 fit into gaps between adjacent stator windings 86,adjacent tabs 102 of the end insulator 92, or somewhere in between. Inan embodiment, crown teeth 276 rest against or over ends of insulatinginserts 260. In this manner, the sealing member 268 forms a mechanicalseal that substantially blocks flow of air between the stator assembly70 and the rotor assembly 72, thus reduces entry of debris andcontamination from entering the rotor assembly 72.

Another aspect of the invention is described herein with reference toFIGS. 33A-35.

FIGS. 33A and 33B depict exploded views of the power module 34 adjacentthe motor 28, according to an embodiment. As shown herein, in anembodiment, power module 34 includes a power board 280, a thermalinterface 282, and a heat sink 284 which attach to the rear end of themotor housing 29 via fasteners 291. Power module 34 may be furtherprovided with a clamp ring 290 that acts to clamp and cover the powerboard 280 and act as a secondary heat sink. Power module 34 may bedisc-shaped to match the cylindrical profile of the motor 28.Additionally, power module 34 may define a center through-hole 292 thatextends through the power board 280 to accommodate the rotor shaft 44 insome embodiments. In an embodiment, through-holes 285, 287, and 289similarly extend through the clamp ring 290, thermal interface 282, andheat sink 284, as further described later.

In an embodiment, power board 280 is a generally disc-shaped printedcircuit board (PCB) with six power transistors 294 that power the statorwindings 86 of the motor 28, such as MOSFETs and/or IGTBs, on a firstsurface 295 thereof. Power board 280 may additionally include othercircuitry such as the gate drivers, bootstrap circuit, and all othercomponents needed to drive the MOSFETs and/or IGTBs. In addition, powerboard 280 includes a series of positional sensors (e.g., Hall sensors)322 on a second surface 297 thereof, as explained later in detail.

In an embodiment, power board 280 is electrically coupled to a powersource (e.g., a battery pack) via power lines 299 for supplying electricpower to the transistors 294. Power board 280 is also electricallycoupled to a controller (e.g., inside control unit 11 in FIG. 2) viacontrol terminal 293 to receive control signals for controlling theswitching operation of the transistors 294, as well as providepositional signals from the positional sensors 322 to the controller.The transistors 294 may be configured, for example, as a three-phasebridge driver circuit including three high-side and three low-sidetransistors connected to drive the three phases of the motor 28, withthe gates of the transistors 294 being driven by the control signalsfrom the control terminal 293. Examples of such a circuit may be foundin US Patent Publication No. 2013/0342144, which is incorporated hereinby reference in its entirety. In an embodiment, power board 280 includesslots 298 for receiving and electrically connecting to the inputterminals 104. In an embodiment, slots 298 may be defined and spreadaround an outer periphery of the power board 280. The outputs of thetransistors bridge driver circuit is coupled to the motor 28 phases viathese input terminals 104.

As those skilled in the art will appreciate, power transistors 294generate a substantial amount of heat that need to be transferred awayfrom the power module 34 in an effective manner. In an embodiment, heatsink 284 is provided on the second surface 297 of the power board 270for that purpose. In an embodiment, heat sink 284 is generallydisc-shaped, square-shaped, or rectangular shaped, with agenerally-planer body having a substantially flat first surface 340facing the power board 282 and extending parallel thereto. The secondsurface 341 of the heat sink 284 may also be flat, as depicted herein,though this surface may be provided with fins to increase the overallsurface area of the heat sink 284. The size and width of the heat sink284 may vary depending on the power requirements of the tool and thusthe type and size of transistors 294 being used. It is noted, however,that for most 60V power tool applications, the width of the heat sink284 is approximately 1-3 mm.

In an embodiment, thermal interface 282 may be a thin layer made ofSil-Pad® or similar thermally-conductive electrically-insulatingmaterial. Thermal interface 282 may be disposed between the heat sink284 and the power board 280.

In an embodiment, heat sink 284 and thermal interface 282 include slots342 and 343 on their outer periphery to allow a passage for inputterminals 104 to be received within slots 298 of the power board 280.Slots 342 are generally larger than slots 298 to avoid electricalcontact between the heat sink 284 and the terminals 104.

In an embodiment, positional sensors 322 are disposed at a distant onthe second surface 297 of the power board 280, around a periphery of thethrough-hole 292. Where a through-hold 292 does not exist, thepositional sensors 322 are still provided at a distant near a middleportion of the second surface 297 of the power board 280 to detect amagnetic position of the rotor assembly 72, as will be discussed laterin detail. In order to allow the positional sensors 322 to have exposureto the motor 28, irrespective of whether power board 280 includes athrough-hole 292, heat sink 284 and thermal interface 282 are providedwith through-holes 287 and 289 large enough to accommodate thepositional sensors 322. In an embodiment, the through-holes may becircular (e.g., through-hole 287) semi-circular (e.g., through-hole289), or any other shape needed to allow the positional sensors 322 tobe axially accessible from the motor 22. In an embodiment, through-hole287 on the heat sink 284 has a radius that is approximately 1.5 to 3times the radius of through-hole 292 on the power board 280.

FIGS. 34 and 35 depict two alternative exemplary embodiments of themounting mechanism and associated components of the power module 34 andmotor housing 29.

In FIG. 34, where the heat sink 284 is disc-shaped of substantially thesame size as the power board 280, a series of fastener receptacles 359are provided on rear end of the motor housing 29 approximately half-waybetween the shaft 44 and the outer periphery of the motor housing 29. Aseries of corresponding through-holes 361 are provided on the powermodule 34, allowing fasteners 290 to securely fasten the power module 34to the fastener receptacle 359 of the motor housing 29. In anembodiment, individual components of the power module 34 may be heldtogether via fasteners 355 prior to assembly of the power module 34 ontothe motor housing 29. Alternatively, the components of the power module34 may be assembled onto motor housing 29 and held together viafasteners 291 in a single step.

In FIG. 35, where the heat sink 284 is rectangular-shaped with a largersurface area than the power board 280, fastener receptacles 358 areprovided near the outer periphery of the motor housing 29. A series ofcorresponding through-holes 360 are provided on the four corners of theheat sink 284. In this embodiment, the components of the power module 34are held together via fasteners 355 prior to the assembly of the powermodule 34 onto the motor housing 29. Then, fasteners 291 are receivedthrough the through-holes 260 to securely fasten the power module 34onto the fastener receptacle 358 of the motor housing 29.

In an embodiment, as shown in both FIGS. 34 and 35, the rear end of themotor housing 29 is provided with alignment posts 350 projecting formits outer periphery towards the power module 34 for proper alignment ofthe power module 34. The power module is similarly provided withcorresponding slots, or through-holes 352 to receive the posts 350therein during the assembly process. Also, the rear end of the motorhousing 29 is provided with a series of openings 309 through which theinput terminals 101 of the stator assembly project outside the rear endof the motor housing 29.

According to a further embodiment, as shown in FIGS. 36, 37A and 37B,insulator pads 300 are disposed in between the motor housing 29 and thepower module 34 around the input terminals 104. The pads 300 provideinsulation between the input terminals 104 and the heat sink 284 toreduce the risk of electrical short between the two due to contaminationof the components. In an embodiment, each pad 300 includes a slot 302arranged to receive the terminal 101 therethrough. Each pad 300 sits ona substantially planar platform 301 provided on the rear portion of themotor housing 29 with the terminal penetrating therein. In order toprevent the pads 300 to add to the total length of the tool, in anembodiment, the heat sink 284 is provided with cutout regions 302corresponding to the shape of the pads 300, typically provided on theouter periphery of the heat sink 284. The insulator pads 300 are shapedto be contained within the cutout regions 302, thereby providingelectrical insulation between the input terminals 104 and the heat sink284 in both the axial and radial directions. Each pad 300 is configuredto fit into the cutout regions 303 of the heat sink 284.

Referring now to FIG. 38, a perspective view of the stator assembly 70(not including the stator windings) is depicted with the input terminals104 disassembled. FIG. 39 depicts a zoomed-in view of the statorassembly 70 showing the interface between the terminals 104 and thepower module 34. According to an embodiment, each input terminal 104 hasa generally planar retention portion 306 including two legs 305configured for coupling with the receiving slot 106 of the retentionmember 108, such as with a snap-fit. The retention portion 306 includesa generally J-shaped wire-receiving member 308. During the assemblyprocess, after an input terminal 104 is inserted into a correspondingreceiving slot 106, an end of a corresponding stator winding (not shownherein) is routed around the end insulator 92 towards the input terminal104 and wrapped around the wire-receiving member 308 to electricallyconnect the input terminal 104 with the corresponding winding 86. Agenerally rectangular tab portion 310 extends from the retention portion306 at about a 90° offset for connection to the power module 34. Whenthe stator assembly 70 is assembled into the motor housing 29, the tabportions 310 extend through openings 309 (see FIGS. 34 and 35) of themotor housing 29. When the power module 34 is assembled at the rear endof the motor housing 29, the tab portions 310 are tightly receivedinside slots 298 in the power board 280, as described above, tooperatively connect to the power module 34 for communication of powerfrom the power module 34 to the windings 86. The power module includesmetal routings (not shown) that connect the respective terminal 104 tothe appropriate transistors 294. In this way, the input terminals 104provide direct power connectivity between the stator assembly 70 and thepower module 34 without use of any additional wires, which tend to bedifficult to rout and install during the assembly process. In addition,the terminals 101 provide improved alignment for easier and quickerassembly by insuring that the power module 34 is properly orientatedwith the motor housing 29.

Another aspect of the invention is described herein in reference toFIGS. 40-42.

As previously discussed, and shown in FIG. 40, power module 34 isdesigned to allow positional sensors 322 disposed on the second surface297 of the power board 280 to be exposed to the motor 28. Specifically,heat sink 284 and thermal interface 282 include through-holes 287 and289 shaped and sized to allow the positional sensors 322 to be axiallyexposed towards the motor 28.

Conventionally BLDC motors are provided with sense magnets positionedadjacent the rotor and mounted on the rotor shaft. The sense magnets mayinclude, for example, four magnets disposed on a ring with adjacentmagnets having opposite polarities, such that rotation of the magnetring along with the motor rotor allows positional sensors to sense thechange in magnetic polarity their vicinity. The problem with theconventional BLDC motor designs, however, is that positional sensorshave to be arranged within the motor in close proximity to the sensemagnet ring.

According to an embodiment, as shown in FIGS. 41 and 42, in order toprovide positional sensors 322 with means to detect the rotationalposition of the rotor shaft 44, sense magnet 324 (configured as a sensemagnet ring including two or four magnets) is disposed near the end ofthe rotor shaft 44 such that, when the rotor assembly 72 is assembledinto the motor housing 28, the sense magnet 324 sits within (or projectsout of) a corresponding through-hole 320 in the rear end of the motorhousing 28. This arrangement allows the sense magnet 324 to be disposedsubstantially close to the positional sensors 322. In an embodiment, thesense magnet 324 may be at least partially received within thethrough-hole 287 of the heat sink 284. In an embodiment, the motorhousing 28 is provided with a ring-shaped labyrinth 326 around thethrough-hole 320 to substantially block debris and contamination fromentering into the rotor assembly 72 from the area around the sensemagnet 324.

In an embodiment, in order to facilitate the assembly of the rotorassembly 72 into the motor housing 28 as described above, the rearbearing 78 is disposed between the rotor lamination stack 76 and thesense magnet 324. The bearing pocket 266 is formed inside the motorhousing 28 around the through-hole 320. As the rear bearing 78 isreceived and secured inside the bearing pocket 266, the sense magnet 324is received inside the through-hole 320, projecting at least partiallyout of the rear end of the motor housing 28.

Some of the techniques described herein may be implemented by one ormore computer programs executed by one or more processors residing, forexample on a power tool. The computer programs includeprocessor-executable instructions that are stored on a non-transitorytangible computer readable medium. The computer programs may alsoinclude stored data. Non-limiting examples of the non-transitorytangible computer readable medium are nonvolatile memory, magneticstorage, and optical storage.

Some portions of the above description present the techniques describedherein in terms of algorithms and symbolic representations of operationson information. These algorithmic descriptions and representations arethe means used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. These operations, while described functionally or logically, areunderstood to be implemented by computer programs. Furthermore, it hasalso proven convenient at times to refer to these arrangements ofoperations as modules or by functional names, without loss ofgenerality.

Certain aspects of the described techniques include process steps andinstructions described herein in the form of an algorithm. It should benoted that the described process steps and instructions could beembodied in software, firmware or hardware, and when embodied insoftware, could be downloaded to reside on and be operated fromdifferent platforms used by real time network operating systems.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

The invention claimed is:
 1. A brushless DC (BLDC) motor including astator assembly and a rotor rotatably arranged inside the stator, thestator assembly comprising: a generally-cylindrical lamination stackincluding a stator ring and a plurality of stator teeth extendingradially inwardly from the stator ring towards a center bore, the centerbore arranged to receive the rotor therein; an end insulator disposed atan and of the lamination stack, the end insulator including agenerally-cylindrical outer ring and a plurality of teeth portionsextending radially inwardly from the outer ring towards a center of theend insulator, the outer ring and the plurality of teeth portioncorresponding to the stator ring and the plurality of stator teeth; anda plurality of stator windings wound around the plurality of statorteeth and the corresponding plurality of teeth portion of the endinsulator; wherein each tooth portion includes an outer face having asloped portion sloped at an angle in the direction of the outer ring ofthe end insulator to bias the plurality of stator windings towards theouter ring, wherein the sloped portion extends from approximately aninner end of the tooth portion towards the outer ring, and wherein theouter face of the tooth portion further includes flat portions along twolongitudinal sides of the sloped portion.
 2. The motor of claim 1,wherein the sloped portion occupies approximately a third of a totalwidth of the outer face of the tooth portion.
 3. The motor of claim 1,wherein the sloped portion includes an angle of 2 to 10 degrees from theouter face of the tooth portion.
 4. The motor of claim 1, wherein thetooth portion occupies approximately an entire width of the outer faceof the tooth portion.
 5. The motor of claim 1, wherein an end of thesloped portion near the outer ring includes a recessed portion recessedfrom a plane of the outer face of the tooth portion.
 6. The motor ofclaim 1, wherein the outer face of the tooth portion further includes aflat portion located between an inner end of the tooth portion and thesloped portion.
 7. The motor of claim 6, wherein a radial length of theflat portion is 15% to 25% of the radial length of the sloped portion.8. The motor of claim 1, wherein the sloped portion includes a firstsloped portion extending from approximately an inner end of the toothportion at a first angle with respect to the outer face of the toothportion, and a second sloped portion extending from the first slopedportion at a second angle with respect to the outer face of the toothportion that is smaller than the first angle.
 9. A power tool comprisinga housing and a brushless DC (BLDC) motor disposed within the housing,the motor including a stator assembly and a rotor rotatably arrangedinside the stator, the stator assembly comprising: agenerally-cylindrical lamination stack including a stator ring and aplurality of stator teeth extending radially inwardly from the statorring towards a center bore, the center bore arranged to receive therotor therein; an end insulator disposed at an and of the laminationstack, the end insulator including a generally-cylindrical outer ringand a plurality of teeth portions extending radially inwardly from theouter ring towards a center of the end insulator, the outer ring and theplurality of teeth portion corresponding to the stator ring and theplurality of stator teeth; and a plurality of stator windings woundaround the plurality of stator teeth and the corresponding plurality ofteeth portion of the end insulator; wherein each tooth portion includesan outer face having a sloped portion sloped at an angle in thedirection of the outer ring of the end insulator to bias the pluralityof stator windings towards the outer ring, wherein the sloped portionextends from approximately an inner end of the tooth portion towards theouter ring, and wherein the outer face of the tooth portion furtherincludes flat portions along two longitudinal sides of the slopedportion.
 10. The power tool of claim 9, wherein the sloped portionoccupies approximately a third of a total width of the outer face of thetooth portion.
 11. The power tool of claim 9, wherein the sloped portionincludes an angle of 2 to 10 degrees from the outer face of the toothportion.
 12. The power tool of claim 9, wherein the tooth portionoccupies approximately an entire width of the outer face of the toothportion.
 13. The power tool of claim 9, wherein an end of the slopedportion near the outer ring includes a recessed portion recessed from aplane of the outer face of the tooth portion.
 14. The power tool ofclaim 9, wherein the outer face of the tooth portion further includes aflat portion located between an inner end of the tooth portion and thesloped portion.
 15. The power tool of claim 14, wherein a radial lengthof the flat portion is 15% to 25% of the radial length of the slopedportion.
 16. The power tool of claim 9, wherein the sloped portionincludes a first sloped portion extending from approximately an innerend of the tooth portion at a first angle with respect to the outer faceof the tooth portion, and a second sloped portion extending from thefirst sloped portion at a second angle with respect to the outer face ofthe tooth portion that is smaller than the first angle.